Modern communication systems enable subscribers, when moving temporarily to a different place of residence, to personalize the “visited” communication terminal at the new place of residence to match their own communication terminal. Such personalization means that the subscriber is able to use his existing user settings, e.g. user-specific feature activations or the settings on his own user interface, at the visited communication terminal, without having to carry out all these settings separately at the new communication terminal.
In order to initiate personalization of this type, the subscriber registers at the visited communication terminal by inputting a user number assigned to him—for example his subscriber number—and a personal identification number (PIN). Registration is also often carried out by means of a chipcard instead of inputting a user number and PIN.
The relevant feature for supporting this temporary or even long-term switch is also known within the circle of experts as “mobile subscriber”. The term “mobile subscriber” is also used below to refer to the subscriber using this feature.
Modern communication systems are increasingly moving over to using continuous data streams, e.g. for voice and video communication, and data for controlling communication links via packet-oriented networks. This technology is used, for example, as the basis for so-called Internet telephony, often also known as “Voice over Internet Protocol” (VoIP). As is known, packet-oriented networks include LANs (Local Area Network), MANs (Metropolitan Area Network), WANs (Wide Area Network) or even the Internet, which facilitates worldwide access to data transferred in packets.
In the telecommunications field, communication devices which, as well as conventional communication links based on a circuit-switching principle, also support the VoIP process and connection of suitably configured communication terminals—known as VoIP communication terminals—are becoming increasingly familiar.
In contrast to local communication systems based on so-called peer-to-peer configurations, in which both the communication control and the call-processing control between the communication terminals takes place without a central communication device, the aforementioned communication devices, which have been expanded to include a VoIP functionality, also adopt, in VoIP communication terminals, a central control function with regard to the switching of communication connections.
For this purpose each VoIP communication terminal is registered at its assigned communication device with appropriate subscriber data, such as—for example—the subscriber number, subscriber authorizations, etc. Each VoIP communication terminal is therefore assigned, via the packet-oriented network, to a communication device assigned to it and likewise connected to the packet-oriented network. The packet-oriented network generally incorporates the entire communication system, i.e. the packet-oriented network can be accessed from any point in the communication system. In turn, any potential communication partner may be reached from any possible access point.
The personalization of a visited communication terminal by a mobile subscriber to a communication terminal of his choice is also known in a communication system consisting of a network of multiple communication devices. In a network of this type, a communication device is frequently assigned to a particular subscriber as the so-called home node. At the home node are stored the subscriber's individual configuration data, such as—for example—his subscriber number, authorization information, feature activations, etc.
For example, a method is known from the unexamined German application DE 199 46 976 A1, that permits so-called inter-node user mobility—i.e. the facility to switch from one communication terminal assigned to a first communication device to a visited communication terminal assigned to a second communication device—between communication terminals within a communication system, whilst keeping the individual user settings. When a mobile subscriber logs on to the visited communication terminal, which is assigned to the second communication device, user-specific configuration data is transferred to the second communication device from the first communication device which is assigned to the user as the “home node”, whereupon the setting of the user configuration for the mobile subscriber is initiated on the basis of the transmitted configuration data.
Once the user configuration has been set, communication devices—to which communication terminals are assigned via a permanently allocated line and a line unit permanently allocated to the communication terminal in question—take over the call-processing and communication control functions without the interaction of the mobile subscriber's home node. By registering to a communication terminal assigned to a different communication device, the mobile subscriber has apparently “switched” the communication device, whereby no changes occur with regard to his subscriber number and caller identification with outgoing calls.
The above-mentioned method is thus based on the transfer of user-specific configuration data from the communication device that stores this configuration data—the home node—to the communication device assigned to the visited communication terminal. Even though extensive personalization of the visited communication terminal is possible with the help of the user-specific configuration data, in particular—for example—in the form of an allocation of the subscriber's personal authorizations, personal call data recording and call charge assignment, certain group and team functions, such as—for example—a team function technically known as “executive/secretary configuration”, are however not possible due to the switching of the communication device from the home node to the communication device assigned to the visited communication terminal. This means that some important functions and features cannot be used by mobile subscribers at other communication devices visited by them.